Method of manufacturing door frame for wind tower

ABSTRACT

Disclosed herein is a method of manufacturing a door frame for a wind tower. The method includes a first step of forging a circular planar substance, thereby forming a through hole in a central portion of the substance, a second step of heating the substance that was processed in the first step, a third step of ring-rolling the heated substance around the through hole in an annular shape such that a circumstance of a center hole of the substance is equal to a length of a center line of the door frame, a fourth step of upset-forging the annular substance so that opposite sides of the substance are pressed to form linear sections, and a fifth step of fine-finishing the substance that was processed by the fourth step, thus completing the door frame.

FIELD OF THE INVENTION

The present invention relates generally to methods of manufacturing doorframes for wind towers and, more particularly, to a method ofmanufacturing a door frame installed in a wind tower.

BACKGROUND OF THE INVENTION

Limited oil resources will become exhausted someday. Thus, a lot ofresearch has recently been done into alternative energies which cansubstitute for the resources and many different kinds of technologiesaiming to develop alternative energy have been proposed. Particularly,many technologies for generating electricity from natural energy sourceshave been studied because the conclusion was reached that natural energysources, such as the sun, wind, water, etc., are almost infinite and canbe used as ideal alternative energy sources. A wind power generationtechnology in which blades are rotated by wind power so that electricityis generated is at the stage of practical application.

However, in wind power generation, a vast land area and large expensesare required to install single wind power generating equipment andsystem.

Various ways to reduce the production cost of wind power generatingequipment have recently been proposed.

FIG. 1 is a perspective view showing a typical wind tower.

Typically, a propeller 5 is provided on the upper end of a wind tower 1and connected to a generation part 4. To allow a worker to inspect thegeneration part 4, a door 2 with a door frame is installed at apredetermined position in the wind tower 1.

As shown in FIG. 2, forming the door frame 20 includes forging a rawsubstance 10 (a slab or ingot) in a planar shape, rough-machining thesubstance 10, and fine-finishing it thereby producing a final product.

However, in the conventional manufacturing method, a large amount ofcut-out portions 12 are removed from the raw substance duringrough-machining and fine-finishing, thus increasing waste of materialand the time it takes to manufacture it.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a method of manufacturing a door frame for awind tower which can reduce the cost and time required to manufacturethe door frame.

In order to accomplish the above object, the present invention providesa method of manufacturing a door frame for a wind tower, including afirst step of forging a circular planar substance, thereby forming athrough hole in a central portion of the substance, a second step ofheating the substance that was processed in the first step, a third stepof ring-rolling the heated substance around the through hole in anannular shape such that a circumstance of a center hole of the substanceis equal to a length of a center line of the door frame, a fourth stepof upset-forging the annular substance so that opposite sides of thesubstance are pressed to form linear sections, and a fifth step offine-finishing the substance that was processed by the fourth step, thuscompleting the door frame.

Preferably, a ratio (t/w) of a thickness (t) to a width (w) of thesubstance processed by the fine-finishing may range from 0.5 to 1.

In the fifth step, a length ratio (a/b) of the linear section (a) formedin each of the opposite sides of the substance to a curved section (b)may be 0.7 or more.

Further, a ratio (w/L) of a width (w) to a height (L) of the substanceprocessed by the fine-finishing may be 0.1 or more.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a perspective view showing a typical wind tower;

FIG. 2 is a view illustrating an example of a conventional method ofmanufacturing a door frame for a wind tower;

FIGS. 3A through 3E are views illustrating a method of manufacturing adoor frame for a wind tower, according to an embodiment of the presentinvention;

FIGS. 4A and 4B are views comparing a final product to an intermediateproduct which has been processed at a third step of the door framemanufacturing method according to the embodiment of the presentinvention;

FIG. 5 is a plan view of a door frame for a wind tower which ismanufactured by the door frame manufacturing method according to thepresent invention; and

FIG. 6 is a perspective view of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a preferred embodiment of the present invention will bedescribed in detail with reference to the attached drawings.

FIGS. 3A through 3E are views illustrating a method of manufacturing adoor frame for a wind tower, according to the embodiment of the presentinvention.

As shown in FIGS. 3A through 3E, the door frame manufacturing methodaccording to the present invention includes five steps. As shown in FIG.3A, in a first step, a through hole is formed through a central portionof a circular planar substance by a forging process. In a second step,the substance that has been processed in the first step is heated. Asshown in FIG. 3B, the substance that has been heated at the second stepis shaped into an annular shape around the through hole by a ringrolling method, in a third step. As shown in FIGS. 3C and 3D, in afourth step, opposite sides of the annular substance are pressed byupset forging to form linear sections therein. As shown in FIG. 3E, in afifth step, the substance that has been processed in the fourth step isfine-finished, thus producing a door frame.

In detail, first, before the first step, the substance is heated to apredetermined temperature by a furnace and machined in a circular planarshape by a rough-shaping process which is a pre-forging process.

The substance that has passed through the preliminary step is processedby the first step so that the through hole 110 is formed through thecentral portion of the substance by punching.

Subsequently, the second step is performed, which is carrying out aheating process required to conduct the ring rolling process of thethird step. In the third step, the diameter of the annular substance isextended.

The ring rolling method refers to a method in which an annular substanceis pressed by a forging machine, including a main roll, a rollingmandrel and an axle roll which is provided at each of upper and lowersides, so that the diameter of the substance is extended into a desiredshape.

Here, the circumference of the center hole of the substance that hasbeen processed by the ring rolling method in the third step correspondsto the length of a center line of the door frame which is a finalproduct.

FIGS. 4A and 4B are views comparing the final product to the substancethat has been processed in the third step of the door framemanufacturing method according to the embodiment of the presentinvention.

The present invention must be designed such that the circumstance of thecenter hole 14 of the substance 10 of FIG. 4A that has been processed inthe third step is the same as the length of the center line 24 of thedoor frame 20 of FIG. 4B which is the final product.

Subsequently, as shown in FIGS. 3C and 3D, in the fourth step, theopposite sides of the annular substance are pressed by upset forging sothat the linear sections are formed in the substance. As shown in FIG.3E, the fifth step includes fine-finishing the substance that has beenprocessed in the fourth step, thus completing the door frame.

Meanwhile, in the fourth step, the substance 100 must be re-heated to apredetermined temperature when upset forging it. The heated substance100 is placed on a lower mold 50, and an upper mold 60 is pressed by apress so that a linear section is formed in each of the opposite sidesof the substance 100. In the fifth step, the substance is fine-finished,thus completing the final product.

Several conditions must be met in order for upset forging to be used tomake the linear sections.

A ratio (t/w) of a thickness t to a width w of the substance, which hasbeen processed in the fifth step which is the final step, must rangefrom 0.5 to 1. A length ratio (a/b) of a linear section a, which isformed in each of the opposite sides of the substance, to a curvedsection b must be 0.7 or more. A ratio (w/L) of the width w to a heightL of the substance must be 0.1 or more.

FIG. 5 is a plan view of the door frame manufactured by the door framemanufacturing method according to the present invention. FIG. 6 is aperspective view of FIG. 5.

As shown in FIG. 5, each of the linear sections a which are formed onthe opposite sides of the substance must be shorter than the curvedsection b (in detail, having an elliptical shape) which is formed ineach of both ends of the substance, and the ratio (a/b) must be 0.7 ormore. If the linear section is excessively long, the substance may bedeformed during the forging process.

Furthermore, if the width w of the substance is excessively small withrespect to the height L of the substance, or if the thickness t of thesubstance is excessively small or large with respect to the width w ofthe substance, the substance may also be deformed during the upsetforging process. Therefore, the ratio (t/w) of the thickness t to thewidth w of the substance must range from 0.5 to 1, and the ratio (w/L)of the width w to the height L of the substance must be 0.1 or more.

As described above, a method of manufacturing a door frame for a windtower according to the present invention includes shaping a substance ina shape similar to that of the door frame through ring-rolling andupset-forging processes, and fine-finishing it, thus completing a finalproduct. Therefore, unlike the conventional art, a rough machiningprocess can be omitted. Thereby, the cost and time required tomanufacture the door frame can be markedly reduced.

The critical technical spirit of the present invention is to provide amethod of a door frame for a wind tower. Although the preferredembodiment of the present invention has been disclosed for illustrativepurposes, those skilled in the art will appreciate that variousmodifications, additions and substitutions are possible, withoutdeparting from the scope and spirit of the invention as disclosed in theaccompanying claims.

What is claimed is:
 1. A method of manufacturing a door frame for a windtower, comprising: forging a circular planar substance, thereby forminga through hole in a central portion of the substance; heating thesubstance processed by the forging; ring-rolling the heated substancearound the through hole in an annular shape such that a circumstance ofa center hole of the substance is equal to a length of a center line ofthe door frame; upset-forging the annular substance so that oppositesides of the substance are pressed to form linear sections; andfine-finishing the substance processed by the upset-forging, thuscompleting the door frame.
 2. The method as set forth in claim 1,wherein a ratio (t/w) of a thickness (t) to a width (w) of the substanceprocessed by the fine-finishing ranges from 0.5 to
 1. 3. The method asset forth in claim 1, wherein in the fine-finishing the substance, alength ratio (a/b) of the linear section (a) formed in each of theopposite sides of the substance to a curved section (b) is 0.7 or more.4. The method as set forth in claim 1, wherein a ratio (w/L) of a width(w) to a height (L) of the substance processed by the fine-finishing is0.1 or more.